1. Field of the Invention
The invention is a method of decolorizing or stabilizing triethanolamine, diethanolamine or monoethanolamine by treatment with an alkylene oxide.
2. Description of Other Related Methods in the Field
Many decolorizing agents now in use remove color by physical adsorption. The most common materials to remove color by this means are represented by charcoals, blacks (such as carbon black), clays and earths. Other compounds remove color by chemical reaction and are frequently more specific as to the materials they can remove color from than the physical adsorption agents. While attempts have been made to predict compound colors, such as by electronegative or steric contributions of substituents to aromatic rings, numerous exceptions to rules relating color to structure require color prediction to be based largely on empirical observations, see Griffiths, John; Colour and Constitution of Organic Molecules; London: Academic Press (1976), pp. 89-90. As a result, attempts to remove color from a specific compound tend to be strictly trial and error operations.
Specific examples may be seen in the decolorization of diethanolamine and triethanolamine. U.S. Pat. No. 3,207,790 describes the decolorization of triethanolamine through the use of sodium or potassium borohydride. U.S. Pat. No. 3,207,790 and 3,159,276 discuss decolorizing ethanolamines with borohydride. Amines may also be decolorized by the use of calcium hydroxide according to U.S. Pat. No. 2,716,136 or with hydrazine in U.S. Pat. No. 2,901,513.